Seismic Response of Single Pylon Cable-Stayed Bridge under Scour Effect

Abstract

For a bridge located in a seismically active and flood-prone region, the occurrence of earthquakes combined with flood-induced scour is a highly possible multihazard event. This study quantifies the scour effect on the seismic performance of a single pylon cable-stayed bridge under bidirectional earthquake excitations. Three-dimensional finite-element models, considering the nonlinear soil–structure interaction, the flexure–shear behavior of the bridge pier, and the hydrodynamic force applied to bridge structures, are built on the OpenSees platform. Several scour depths are considered in this study to represent various scour intensities within the service life of the cable-stayed bridge. The modal analyses indicate that the periods of the few vibration modes (fourth and fifth modes) of the cable-stayed bridge increase as the scour progresses, and the scour effects gradually diminish for higher and lower vibration modes (first, second, and third modes). The results of the nonlinear time history analyses indicate that the moments on the piles increase as scour progresses, while the moment demand of the pier decreases. The moment in the pylon of the scoured bridge is much larger than the intact bridge due to the higher pounding potentials with the increase of scour depth. Obviously, the failure modes of the cable-stayed bridge transform from the pier to the piles and the abutments. In addition, the impact of the hydrodynamic force on the seismic response of the bridge is negligibly small. The findings of this study can be used to guide the seismic design and the retrofitting of cable-stayed bridges under scour-critical conditions.